#zhezhao{
    height: 100%;
    width: 100%;
    background-color: black;
    opacity: 0.5;
    position: fixed;
    left: 0px;
    top: 0px;
    display: none;
}

#ceng{
    border: 1px black solid;
    background-color: white;
    width: 242px;
    position: fixed;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    display: none;
}